Along with progress of information technology, office automation has become a trend. In addition to using computers for processing and storage of large quantities of data, using scanners as output devices of data such as documents, tables, and images can also effectively enhance the efficiency of inputting data. In order to avoid bad situations such as distortion of data inputted into a scanner during the scanning process, the optical path of a scanning head of the scanner must be kept constant. Therefore, requirement of transmission stability of a scanner's transmission mechanism is very high.
As shown in FIG. 1, in a fixing seat of main transmission shaft of a conventional transmission mechanism, a bearing plate 14 is disposed on a motor device 12. A plurality of screws 16 are used to fixedly lock the bearing plate 14 on a scanner bottom seat 18. A timing pulley 20 is pivotally disposed on the bearing plate 14. The timing pulley 20 is driven to rotate by the motor device 12. A belt 22 is used to wind around the timing pulley 20 and an idle pulley 24 so that a scanning head (not shown) can be driven to move by means of transmission of the belt 22.
When the above belt 22 moves, the axis of the timing pulley 20 will bear the entire tension of the belt 22 to easily generate torsion effect. Moreover, the bearing plate 14 is generally fixed on the bottom seat 18 made of plastic, as shown in FIG. 2. When the bottom seat 18 is softened by high temperature due to long-time operation of the belt 22, the axis of the timing pulley 20 pivotally disposed on the bearing plate 14 will easily deform to reduce the tension of the belt 22, hence affecting stability of motion of the scanning head to deteriorate resolution quality of image. On the other hand, in order to let the timing pulley 20 on the bearing plate 14 keep stable when being operated, more screws 16 are required to steadily and exactly lock the bearing plate 14 on the scanner bottom seat 18, hence resulting in a higher production cost.
Accordingly, in consideration of the above problems, the present invention proposes a fixing seat of main transmission shaft of a scanner having high stability and a low manufacturing cost.